Prep ingredients per the instructions above.
Mix together the water and cucumber slices. Refrigerate until ready to serve.
Cook pasta: Fill a saucepan with water. Bring to a boil and cook the pasta according to package instructions.
Make the cheese sauce: In a saucepan on medium heat, melt the butter. Add in the flour and whisk together. Once combined, gradually whisk in the milk and cheese. Whisk regularly, so the cheese melts and the sauce thickens up and becomes smooth. Season with salt and pepper to taste.
Make sloppy Joe: In a nonstick pan over medium heat, cook the beef until no longer pink and drain the grease. Stir in the ketchup, water, Worcestershire sauce, mustard, and garlic powder, and season with salt and pepper. Bring to a simmer until the sauce is well combined and thickened.
Lightly toast the roll.
Assemble: Spoon the sloppy joe onto the bread. Top with red onion.
Serve: Enjoy the sloppy joe with mac and cheese, celery sticks, ranch, watermelon and cucumber water.